Interactions between Neurokinin B and kisspeptin in mediating estrogen feedback in healthy women

Abstract

Context: Kisspeptin and neurokinin B (NKB) are obligate for normal gonadotropin secretion, but their hierarchy is unexplored in normal women. Objective: To investigate the interaction between kisspeptin and NKB on estrogen-regulated LH secretion. Design: Women were treated with neurokinin-3 receptor (NK3R) antagonist followed by transdermal estradiol to induce LH secretion 48 hours later, with kisspeptin-10 or vehicle infusion during estrogen administration in a 2-way crossover study. Setting: Clinical research facility. Patients or other participants: Healthy females with regular menses. Intervention(s): NK3R antagonist AZD4901 40 mg twice daily orally was taken from cycle day 4-6 for 6 days (n = 10, with 10 no treatment controls). Transdermal estradiol patches (200 μg/d) were applied after 5 days of NK3R antagonist treatment. At 24-hour estradiol treatment, women were randomized to 7-hour kisspeptin-10 (4 μg/kg/h) or vehicle iv infusion, with the alternate infusion in a subsequent cycle. Main outcome measure(s): Plasma gonadotropin and estradiol secretion. Results: After an initial suppression, LH secretion was increased 48 hours after estradiol treatment. Kisspeptin-10 increased LH secretion during the inhibitory phase, and LH remained elevated beyond the discontinuation of kisspeptin-10 infusion. NK3R antagonist decreased LH pulse frequency (0.5 ± 0.2 vs 0.7 ± 0.2 pulses/h, P